Compensating device for volumetric pumps

ABSTRACT

A compensating device for volumetric pumps, comprising: a storage tank (2) predisposed for being connected to the delivery line (O) of a pump (P) and to a source of pressurized gas (A); a control valve (3) arranged for opening or closing the connection between the tank (2) and the source of pressurized gas (A); a control module (4) connected to the control valve (3). The device comprises a level sensor (5) associated with the tank (2) for detecting a threshold level for a liquid within the tank (2) and connected to the control module (4) for transmitting to the module (4) at least one operating signal indicating a liquid level higher than the threshold level. The control module (4) is configured to determine the opening of the control valve (3) in the presence of said operating signal and to determine the closing of the control valve (3) in the absence of said operating signal.

The object of the present invention is a compensating device forvolumetric pumps.

The invention finds advantageous use in compensating pulsations in theflow rate and pressure at the delivery point of a piston pump,particularly in the presence of abrasive and/or corrosive liquids, asfor example in plants for processing ceramic slips.

High power piston pumps that feed the ceramic slip along a processingline are normally used in such plants. Storage tanks placed incommunication with the delivery line of the pump are used to compensatefor the pulsations in the flow rate and pressure at the delivery pointof the pump. These tanks are filled partly with the pumped liquid andpartly with the air compressed to a predetermined pressure. To reducethe pulsations in pressure and flow rate at the delivery point of thepump, the pressure inside the tank must remain substantially constant.

The compensating tanks are substantially managed based on the pressureof the air inside the tank. For this purpose, a pressure gauge is placedin communication with the tank and connected to a control panel thatdetermines the opening and closing of a compressed air supply valve. Ifthe pressure drops below a given threshold value, the control panelcommands the opening of the valve so as to inject air into the tankagain.

The use of a pressure gauge can involve several drawbacks. In fact,operation of the pressure gauge can be negatively affected by thepresence of impurities and sudden fluctuations in temperature, therebyjeopardizing proper control of the pressure inside the tank.

The aim of the present invention is to offer a compensating device forvolumetric pumps that makes it possible to improve the characteristicsof the devices that are currently available.

Characteristics and advantages of the present invention will become moreapparent in the following detailed description of an embodiment of theinvention concerned illustrated by way of non-limiting example in FIG. 1attached hereto, which is a schematic view of the device according tothe present invention.

With reference to the figure, the compensating device according to thepresent invention comprises a storage tank (2) predisposed to beconnected to the delivery line (O) of a pump (P) and to a source ofpressurized gas (A). The pump (P) is for example a piston pump. Thesource of pressurized gas (A) is for example a compressed air circuit,normally present in all industrial plant systems. The tank (2) isequipped with a pressure gauge (7) for safety and control functions.

A control valve (3) is interposed between the tank (2) and the source ofgas (A). This control valve (3) is arranged for opening or closing theconnection between the tank (2) and the source of gas (A), taking on anopening configuration and a closing configuration, respectively. Thecontrol valve (3) is connected to a control module (4) that activatesthe control valve (3) in the opening and closing configurations.

The compensating device comprises a level sensor (5) associated with thetank (2). The level sensor (5) is configured to detect a threshold levelfor the liquid present inside the tank (2).The level sensor (5) is alsoconnected to the control module (4) for transmitting to the module (4)at least one operating signal indicating a level of liquid higher thanthe threshold level.

In other words, the level sensor (5) is located at a given height on thetank (2), so as to detect the presence or absence of liquid at thatgiven height, which corresponds to the threshold level. If the sensor(5) detects the presence of liquid, this means that level of liquidinside the tank (2) is equal to or higher than the threshold level andthe sensor (5) transmits its operating signal. If the sensor (5) doesnot detect the presence of liquid, then the level of liquid inside thetank (2) is below the threshold level and the sensor (5) stopstransmission of its operating signal and transmits a signal differingfrom the operating signal.

The sensor (5) is structured so as to directly measure the level of theliquid inside the tank (2). In other words, at least one part or onezone of the sensor (5) is placed in contact with or can enter intocontact with the liquid inside the tank (2).This makes it possible toobtain a substantially instantaneous and direct measurement of the levelof liquid inside the tank (2).

The sensor (5) is preferably a capacitive type of sensor, but it couldbe of another type such as a float sensor.

The control module (4) is configured to determine the opening of thecontrol valve (3) in the presence of the operating signal transmitted bythe sensor (5) and to determine the closing of the control valve (3) inthe absence of said operating signal.

The opening of the control valve (3) enables the introduction ofpressurized gas inside the tank (2).The thrust exerted by the gas on theliquid present in the tank (2) produces the lowering of the liquidlevel. When the level drops below the threshold level, the sensor (5)stops transmitting its operating signal or transmits a signal differingfrom the operating signal, and the control module determines the closingof the control valve (3). In this manner, by determining the opening andclosing of the control valve (3) in relation to the signal transmittedby the level sensor (5), it is possible to keep the liquid level insidethe tank substantially constant, and thus also the volume available forthe air.

Essentially, the device is controlled based on the volume of air presentinside the tank (2), rather than based on the pressure present insidethe tank (2) as is the case in currently available devices. This makesit possible to obviate the use of a pressure gauge for controlling thedevice.

The liquid level inside the tank (2) is detected at predetermined timeintervals. Detection frequency is preferably determined so as to preventexcessive rising of the liquid level and simultaneously preventexcessively frequent activation of the control valve (3).

1. A compensating device for volumetric pumps, comprising: a storagetank (2), predisposed for being connected to the delivery line (O) of apump (P) and to a source of pressurized gas (A); a control valve (3),arranged for opening or closing the connection between the tank (2) andthe source of pressurized gas (A); a control module (4), connected tothe control valve (3); characterized in that: it includes a level sensor(5) associated with the tank (2) for detecting a threshold level for aliquid within the tank (2) and connected to the control module (4) fortransmitting to said module (4) at least one operating signal indicatinga liquid level higher than the threshold level; the control module (4)is configured so as to determine the opening of the control valve (3) inthe presence of said operating signal and to determine the closing ofthe control valve (3) in the absence of said operating signal.
 2. Thecompensating device according to claim 1, wherein the sensor (5) isstructured so as to directly measure the level of the liquid inside thetank (2).
 3. The compensating device according to claim 1, wherein atleast one part or one zone of the sensor (5) is placed in contact withor can enter into direct contact with the liquid inside the tank (2). 4.The compensating device according to claim 1, wherein the level sensor(5) is a capacitive sensor.
 5. A control method for a storage tank (2)predisposed for being connected to the delivery line (0) of a pump (P),comprising the following steps: detecting the level of liquid inside thestorage tank (2); if the level of liquid is higher than a thresholdlevel, allowing the feeding of pressurized gas to the tank (2); if theliquid level is lower than the threshold level, preventing the feedingof pressurized gas to the tank (2)
 6. The method according to claim 5,wherein the liquid level is detected at predetermined time intervals.